The presented project intends to evaluate the role of the fluxes of zinc and calcium associated with hormone secretion and their possible role in the coupling of stimulation to secretion in pancreatic endocrine cells. The so-called principal islets, or Brockmann bodies, of channel catfish (Ictalurus punctatus) consisting of about 50% endocrine cells shall be perfused by adopting techniques known for mammalian pancreases (if available, goosefish (Lophius piscatorius) shall be included in this study). The technique of perfusion avoids artifacts usually encountered with isolation procedures for mammalian islets. It will allow one for the first time to measure fluxes of divalent cations associated with insulin release, glucagon release, and somatostatin release in the intact pancreatic endocrine tissue. At first, the hormonal secretion pattern of fish islet tissue in response to various known secretagogues for mammalian tissue shall be determined by radioimmunoassays, and conditions will be evaluated to specifically or preferentially stimulate the A-, B-, or D-cells. The present project will focus on cation fluxes of the B-cells. The fluxes of zinc and the fluxes of calcium associated with insulin secretion and with stimulus secretion coupling will be measured using a new Zn ions metallochromic indicator, microscale atomic absorption spectroscopy, radioisotope techniques, and zinc-specific chelators. The following processes will be studied: 1) Zinc release associated with insulin release, 2) mechanisms of zinc homeostasis, 3) role of calcium in the coupling of stimulation and secretion, 4) possible calcium release associated with insulin release. Corrections will be made for fluxes caused by the A- and D-cells. Upon completion of the studies on the B-cells, the methodology may consequently be applied to study the A-cells and the D-cells in the same fashion.